Question

va rog e urgent dau coroana​

Answer 1

Răspuns:

Explicație pas cu pas:

suma are: 20-6+1 = 15 termeni

avem:

$\frac{1}{20} < \frac{1}{6} \leq \frac{1}{6}\\\frac{1}{20} < \frac{1}{7} < \frac{1}{6}\\\frac{1}{20} < \frac{1}{8} < \frac{1}{6}\\...\\\frac{1}{20} \leq \frac{1}{20} < \frac{1}{6}$

adunam relatiile:

$15 \cdot \frac{1}{20} < \frac{1}{6} + \frac{1}{7} + \frac{1}{8} + ... + \frac{1}{20} < 15 \cdot \frac{1}{6}$

$\frac{3}{4} < \frac{1}{6} + \frac{1}{7} + \frac{1}{8} + ... + \frac{1}{20} < \frac{5}{2}$

$0,75 < \frac{1}{6} + \frac{1}{7} + \frac{1}{8} + ... + \frac{1}{20} < 2,50$

q.e.d.